Chapter 2 Flashcards

1
Q

What are crystalline material?

A

Atoms formed in periodic 3D arrays (usually metals, ceramics and some polymers)

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2
Q

How does packing affect energy?

A

Dense packing reduces interatomic bond lengths and makes them harder to break

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3
Q

What is crystallinity?

A

A solid material in which atoms are situated in repeating periodic array over large atomic distances

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4
Q

Crystal structure

A

The way that atoms and ions are spacially arranged

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5
Q

What is a unit cell?

A

A unit that can be repeated over space to form the crystalline lattice

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6
Q

What are lattice parameters?

A

3 edge lengths (a, b, c)

3 interaxial angles (alpha, beta, gamma)

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7
Q

Coordination #

A

of neighboring atoms touching particular unit cell in a crystal

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8
Q

What is the atomic packaging factor? (APF)

A

Volume of atoms in a unit cell
______________________________
Volume of a unit cell

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9
Q

Simple cubic crystal structure (SC)

A

rare because of low density

.52% full

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10
Q

Body center cubic (BCC)

A

1 sphere with 8 corners
Coordination number is 8
.68%fill

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11
Q

Face centered cubic (FCC)

A

6 faces 8 cube corners
Coordination number is 12
74% fill

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12
Q

Hexagon closed packed( HCP)

A

Coordination number is 12

74% fill

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13
Q

Point coordinates

A

XYZ axis mapped onto parameters ABC

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14
Q

How to find Crystallographic directions

A

1) determine point coords of vector head and tail
2) head - tail coord
3) normalize differences (divide by A, B or C)
4) reduce to smallest whole numbers
5) enclose indicies in square brackets w/no comma

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15
Q

How to find crystallographic planes

A

1) Find find intercepts of plane through axes(A,B,C)
2) take reciprocal
3) clear fractions
4) reduce to lowest whole numbers

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16
Q

What is linear density?

A

Number of atoms per unit length

LD= #atoms on direction vector
__________________________
Length of direction vector

17
Q

What is linear density?

A

Number of atoms per unit length

LD= #atoms on direction vector
__________________________
Length of direction vector

18
Q

What is planar density?

A

PD= #atoms centered on a plane
___________________________
Area of plane

19
Q

Polycrystalline

A

Composed of many small single crystals or grains

  • properties vary with direction
  • if grains are random isotropic properties
  • if grains are textured anisotrophic
20
Q

What is a grain boundary?

A

Atomic missmatch where 2 grains meet